A known example of a locking device of this type is a technique disclosed in Patent Document 1. In this technique, a locking mechanism is provided on a seat side, and a striker is provided on a vehicle body side. The locking mechanism includes a base plate having a recess capable of receiving the striker, a hook, a pawl and a cam. The hook is rotatably attached to the base plate via a shaft, so that the locking mechanism is in a locked condition in which the striker is held between the hook and the recess of the base plate or in an unlocked condition in which the hook is spaced away from the striker. The pawl and the cam are rotatably attached to the base plate via a common shaft.
A locking spring is positioned between the hook and the pawl. The locking spring biases the hook and the pawl such that the hook and the pawl are stabilized at a rotational position corresponding to the locked condition or the unlocked condition. Also, a thrust spring is positioned between the cam and the base plate. The thrust spring biases the cam in a direction that the hook in the locked condition is further pressed toward a locking direction. As a result, a clearance between the striker and the locking mechanism in the locked condition is forcibly reduced.
Patent Document 1: EP1516771A1